1. Field of the Invention
The present invention relates to a substrate processing system and a substrate processing method for processing substrates, such as semiconductor wafers or glass substrates for LCDs (liquid crystal displays).
2. Description of the Related Art
In general, semiconductor device fabricating process include a step of coating a substrate, such as a semiconductor wafer or a LCD substrate, with a resist solution to form a resist film thereon, a step of transferring a circuit pattern onto the resist film by photolithography, a step of exposing the resist film, and a step of removing resist film from the substrate, which are sequentially performed.
A resist removing method by using ozone, which has little problem on disposal, has been recently proposed for environmental reason. The resist removing method includes a step of accommodating a substrate into a processing chamber, a step of feeding ozone and water vapor into the processing chamber with the interior of the chamber being heated and pressurized thereby water-solubilizing the resist film, and a step of washing off the solubilized resist film by using water in a cleaning chamber.
Japanese patent No. 3174409 discloses a method of transporting wafers in a processing system having plural kinds of processing units. In this patent, the work unit time (the required time interval from the start of a certain process until the start of the next process) of the transport apparatus is set based on the maximum value of the processing time of the processing units The transporting of the wafers is performed every work unit time. Japanese patent No. 2638668 also discloses a method of transporting wafers. In this patent, the transporting of the wafers is performed every work unit tie, however, when carrying the substrate into a processing unit that performs a process in a shorter time than the work unit time, the wafer stands-by for a predetermined time.
However, the above transporting procedures are determined based on the processing time and the time point of starting the processing, but not based on the ability of the processing units. Therefore, if the work unit time is determined as mentioned above, it is necessary to increase the number of the processing units in order to improve the throughput of the processing system.
In a processing system having plural ozone processing vessels and a common ozone generator that supplies ozone to the ozone processing vessels, if the ozone processing vessels are used at random, it is possible that all the ozone processing vessels are used at the same time. Thus, the ozone generator must have an ability of supplying ozone to all the ozone processing vessels at the same time. This results in a large-sized ozone generator and thus a large-sized processing system, and a higher cost of the ozone generator.